CS4525 datasheet(61/98 Pages) CIRRUS

61 / 98 page

DS726PP1

CS4525

6.5

Analog Inputs

Very few components are required to interface between the audio source and the CS4525’s analog inputs,

AINL and AINR. A single order passive low-pass filter is recommended to prevent high-frequency content

from aliasing into the audio band due to the analog-to-digital conversion process. Also, a DC-blocking ca-

pacitor is required as the CS4525’s analog inputs are internally biased to VQ.

The recommended analog input circuit is shown in Figure 28 below will accommodate full-scale input volt-

ages as defined in the Analog Input Characteristics table on page 19. This circuit provides the necessary

high-frequency filtering with a first-order passive low-pass filter that has less than 0.05 dB of attenuation at

24 kHz. It also includes a DC blocking capacitor to accommodate the analog input pins’ bias level.

To interface 2 VRMS input signals with the CS4525’s analog inputs, an external resistor divider is required.

Figure 29 shows the recommended input circuit for 2 VRMS inputs. It includes a -8.4 dB passive attenuator

to condition the input signal for the CS4525’s full-scale input voltage, a first-order passive low-pass filter that

has less than 0.05 dB of attenuation at 24 kHz, and a DC blocking capacitor to accommodate for the analog

input pins’ bias level. The passive attenuator network should be placed as close as possible to the CS4525’s

analog input pins to reduce the potential for noise and signal coupling into the analog input traces.

It should be noted that the external DC blocking capacitor forms a high-pass filter with the CS4525’s input

impedance. Both filters shown above have less than 0.2 dB attenuation at 20 Hz due to this effect. Increas-

ing the value of this capacitor will lower this high-pass corner frequency, and decreasing it’s value will in-

crease the corner frequency.

CS4525

AINL

AINR

1 µF

365

1800 pF

Left Input

1 µF

365

1800 pF

Right Input

100 k

C0G

Figure 28. Recommended Unity Gain Input Filter

CS4525

AINL

100 pF

Left Input

C0G

1 µF

5.62 k

8.06 k

AINR

100 pF

Right Input

C0G

1 µF

5.62 k

8.06 k

Figure 29. Recommended 2 VRMS Input Filter

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